1. Field of the Invention
The present invention relates to a high-pressure fuel pump device comprising a high-pressure pump and a high-pressure regulator.
2. Description of the Prior Art
Diesel engines are widely known as an example of the engine technology that the fuel is injected into its cylinders, which is so called "in-cylinder injection engine" or "direct injection engine". For spark ignition (gasoline) engines also, in-cylinder injection types have recently been proposed. For gasoline engines, there have been recently implemented in-cylinder injection type engines. For example, a high-pressure fuel pump device comprising a high-pressure pump and a high-pressure regulator is disclosed by Japanese Patent Publication No. 2689226.
FIG. 14 is a schematic diagram showing an automobile fuel supply system disclosed by the above publication. In FIG. 14, reference numeral 1 denotes a delivery pipe which is a fuel injection unit, 2 injectors corresponding to the number of the cylinders of an engine 3, 4 a high-pressure fuel pump device attached to the housing of the engine 3, 5 a first housing of the high-pressure fuel pump device 4, 6 a second housing of the high-pressure fuel pump device 4, 7 a connection portion between the first housing 5 and the second housing 6, 8 a high-pressure pump for increasing the pressure of fuel to a high level, and 9 a pumping element 9 incorporated in the first housing 5. The pumping element 9 has such elements as a piston driven by an unshown cam which turns at a half speed of the crank speed of the engine 3 and a cylinder for holding the piston in such a manner that it can reciprocate. Denoted by 10 is an intake valve arranged at the connection portion 7, 11 a discharge valve arranged at the connection portion 7, 12 a high-pressure regulator incorporated in the second housing 6, for adjusting the pressure of fuel by draining part of high-pressure fuel, 13 a low-pressure passage formed in the first housing 5, 14 a low-pressure passage of the second housing side formed in the second housing 6, 15 a high-pressure passage on the first housing side formed in the first housing 5, 16 a first high-pressure passage on the second housing side formed in the second housing 6, 17 a second high-pressure passage on the second housing side formed in the second housing 6, 18 a drain return passage formed in the second housing 6, 19 a fuel tank, 20 a low-pressure pump stored in the fuel tank 19, 21 a low-pressure pipe connected to the outlet portion of the low-pressure pump 20 and to the low-pressure passage 14 on the second housing side, 22 a high-pressure pipe connected to the high-pressure passage 16 on the second housing side and to the inlet portion of the delivery pipe 1, 23 a high-pressure pipe connected to the outlet portion of the delivery pipe 1 and to the second high-pressure passage 17 on the second housing side, 24 a drain return pipe connected to the drain return passage 18 and to the fuel tank 19, and 25 fuel stored in the fuel tank 19. The high-pressure pump 8 is composed of such elements as the first housing 5, the second housing 6, the pumping element 9, the intake valve 10, the discharge valve 11, the low-pressure passage 13 on the first housing side and the high-pressure passage 15 on the first housing side.
A description is subsequently given of the operation of the above fuel supply system. The low-pressure pump 20 sucks the fuel 25 and increases the pressure of the fuel to a low level. This low-pressure fuel 25 is sucked into the pumping element 9 from the low-pressure pipe 21 through the low-pressure passage 14 on the second housing side, the intake valve 10 and the low-pressure passage 13 on the first housing side. The pumping element 9 increases the pressure of the sucked fuel 25 to a high level and discharges it. This high-pressure fuel 25 is supplied to the delivery pipe 1 through the high-pressure passage 15 on the first housing side, the discharge valve 11, the first high-pressure passage 16 on the second housing side and the high-pressure pipe 22. At the fuel injection timing of each cylinder of the engine 3, the corresponding injector 2 injects the high-pressure fuel 25 into the cylinder of the fuel injection timing. When the pressure of the fuel 25 supplied to the second high-pressure passage 17 on the second housing side from the delivery pipe 1 through the high-pressure pipe 23 exceeds a predetermined level set by the high-pressure regulator 12, the high-pressure regulator 12 drains part of the fuel 25 in the second high-pressure passage 17 on the second housing side to control the pressure of the fuel supplied to the delivery pipe 1 from the pumping element 9 at a predetermined high level. This drained fuel 25 is returned to the fuel tank 19 from the drain return passage 18 through the drain return pipe 24.
The above high-pressure fuel pump device 4 of the prior art is structured such that the high-pressure pump 8 includes part of the connection portion 7, that is, the intake valve 10 and the discharge valve 11 are arranged in the connection portion 7 between the first housing 5 and the second housing 6. The high-pressure pump 8 can be a single-cylinder pump having only one piston in the pumping element 9 or a multi-cylinder pump having multiple pistons in the pumping element 9, while the high-pressure regulator 12 can be of a mechanical type for controlling the pressure of fuel to a fixed level or of an electromagnetic type for controlling the pressure of fuel to a variable level. Therefore, with the above mentioned high-pressure pump device 4, it has been difficult to standardize the design of the first housing 5 and/or the second housing 6 per technologies used for the high-pressure pump 8, single-cylinder or multi-cylinder, and per the technologies used for the high-pressure regulator 12, mechanical type or electromagnetic type.